Solvates of selected fenamic acids with substituted pyridines: Structure, thermal stability and desolvation

Mefenamic acid (MA) formed solvates with 2-picoline (2PIC), 3-picoline (3PIC), 4-picoline (4PIC) and 3-chloropyridine (3CLPYR). The solvates crystallized in the space group with the carboxylic acid of MA hydrogen-bonded to the nitrogen of the substituted pyridine. Tolfenamic acid (TFA) formed solvates with 2PIC and 3PIC, the crystal structures successfully solved in the space groups P2₁/n and Pbca, respectively. The fenamate conformation varied depending on the acid and the included solvent. Similarities were observed in the structures involving MA. The two solvate structures of TFA had different packing arrangements. Grinding and slurry experiments were also successful for the preparation of all of the compounds except MA·2PIC. Recrystallization, grinding and slurry investigations of MA and 2PIC yielded a polymorph; the structure was successfully solved in P2₁/n. Additionally, the thermal stability of the solvates was determined. Desolvation experiments were also performed and the resultant powders were analysed using powder X-ray diffraction.Mefenamic acid and tolfenamic acid form solvates with selected substituted pyridines. The crystal structures, thermal stability, desolvation studies and other modes of preparation were also determined.